Async NodeJS

Transcript

1. Async
   sfi 2013 krakow
   Mariusz gil
   

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2. about me
   

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3. about the problem
   

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4. ?
   user browser application
   click request
   response
   ajax
   

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5. database server
   database server
   200 m
   200 m
   400 m
   browser application
   request
   response
   ajax
   

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6. i/o ops are expensive
   l1-cache 3 cycles
   l2-cache 14 cycles
   ram memory 250 cycles
   disk 41 000 000 cycles
   network 240 000 000 cycles
   Source: Ryan Dahl’s 2008.11.08 node.js presentation
   

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7. about the solution
   ...one of them
   

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8. event-driven non-blocking I/O server-side
   javaScript environment based on V8
   

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9. event driven
   

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10. event driven
    

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11. event driven
    

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12. ?
    ? ?
    ? ?
    ? ?
    ?
    ?? ?
    ?
    what the...?
    ?
    

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13. event machine twisted
    

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14. single thread
    events
    queue
    event loop
    callbacks
    

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15. request
    routing
    output
    formatting
    database query api call caching logging
    data
    processing
    

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16. https://npmjs.org/
    node packaged modules
    25 178 packages underscore
    async
    request
    coffee-script
    express
    socket.io
    1.4m downloads
    per day
    

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17. apt-get install python g++ make
    mkdir ~/nodejs && cd $_
    wget -N http://nodejs.org/dist/node-latest.tar.gz
    tar xzvf node-latest.tar.gz && cd `ls -rd node-v*`
    ./configure
    make install
    sudo apt-get install python-software-properties python g++ make
    sudo add-apt-repository ppa:chris-lea/node.js
    sudo apt-get update
    sudo apt-get install nodejs npm
    

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18. var http = require('http');
    http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World\n');
    }).listen(1337, '127.0.0.1');
    console.log('Server running at http://127.0.0.1:1337/');
    

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19. var net = require('net');
    var server = net.createServer(function (socket) {
    socket.write('Echo server\r\n');
    socket.pipe(socket);
    });
    server.listen(1337, '127.0.0.1');
    

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20. var fs = require('fs');
    var data = fs.readFileSync('sample.txt');
    console.log(data);
    var fs = require('fs');
    fs.readFile('sample.txt', function(err, data) {
    console.log(data);
    });
    

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21. var cluster = require('cluster');
    var http = require('http');
    var numCPUs = require('os').cpus().length();
    if (cluster.isMaster) {
    // Fork workers.
    for (var i = 0; i < numCPUs; i++) {
    cluster.fork();
    }
    cluster.on('exit', function (worker, code, signal) {
    console.log('worker ' + worker.process.pid + ' died');
    });
    } else {
    // Workers can share any TCP connection
    // In this case its a HTTP server
    http.createServer(function(req, res) {
    res.writeHead(200,{'Content-Type': 'text/plain'});
    res.end(”hello world\n”);
    }).listen(8000);
    }
    

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22. var mysql = require('mysql');
    var connection = mysql.createConnection({
    host : 'localhost',
    user : 'root',
    password : '',
    socketPath : '/opt/local/var/run/mysql55/mysqld.sock'
    });
    connection.connect();
    var query = connection.query('SELECT * FROM sakila.actor');
    query
    .on('result', function(row) {
    connection.pause();
    function processRow(row, callback) {
    console.log(row);
    callback();
    }
    processRow(row, function() {
    connection.resume();
    });
    })
    .on('end', function() {
    console.log('end\n');
    });
    

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23. var events = require('events');
    var emitter = new events.EventEmitter();
    emitter.on('textEvent', function(data) {
    console.log(data);
    });
    emitter.on('dataEvent', function(data) {
    console.log(data);
    });
    emitter.emit('textEvent', 'Start');
    emitter.emit('dataEvent', new Array(1, 2, 3, 4, 5));
    emitter.emit('textEvent', 'End');
    

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24. lightweight web framework
    like sinatra or silex
    express
    

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25. realtime communication library
    socket.io
    

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26. best use cases
    single page
    a lication lightweight
    API
    ma co ection
    serve
    non-blocking
    I/O a long p l
    

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27. from rails to node mobile backends
    

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28. problems...
    callbacks hell
    libraries
    deployment
    garbage collector
    current version is 0.10.0
    

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29. callback hell
    http://callbackhell.com/
    fs.readdir(source, function(err, files) {
    if (err) {
    console.log('Error finding files: ' + err)
    } else {
    files.forEach(function(filename, fileIndex) {
    console.log(filename)
    gm(source + filename).size(function(err, values) {
    if (err) {
    console.log('Error identifying file size: ' + err)
    } else {
    console.log(filename + ' : ' + values)
    aspect = (values.width / values.height)
    widths.forEach(function(width, widthIndex) {
    height = Math.round(width / aspect)
    console.log('resizing ' + filename + 'to ' + height + 'x' + height)
    this.resize(width, height).write(destination + 'w' + width
    + '_' + filename, function(err) {
    if (err) console.log('Error writing file: ' + err)
    })
    }.bind(this))
    }
    })
    })
    }
    })
    

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30. var async = require('async');
    async.parallel([
    function(callback) { ... },
    function(callback) { ... }
    ], callback);
    var async = require('async');
    async.waterfall([
    function(callback) { ... },
    function(arg, callback) { ... }
    ], callback);
    

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31. thanks!
    feel free to contact with me
    email: mariusz@mariuszgil.pl
    twitter: @mariuszgil
    

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